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Water Quality Standards

July 23, 2010

Water Quality Standards

National water quality standards, based on Article 4 of the Water Supply Law, were revised according to Ordinance 101 issued by the Ministry of Health, Labour and Welfare on May 30, 2003. Article 20 imposes compulsory water quality inspections upon water suppliers with regard to Water Quality Standard Items. In addition to the Water Quality Standard Items, Water Quality Management Target Items were established as matters for attention, and inspections made compulsory on the required items, and efforts to gather new knowledge and information stipulated.
Taking the approach that it is best to revise water quality standards constantly in light of the latest scientific knowledge, on April 1, 2010 the Bureau strengthened its standards with regard to cadmium and its compounds by lowering the reference values from 0.01 mg/L to 0.003 mg/L. In addition, 1,1,2-Trichloroethane was dropped from the Water Quality Management Target Items, while the target values for six substances listed as agricultural chemicals, including isoprothiolane, were revised.
At present, 50 items are listed as Water Quality Standard Items, 27 items as Water Quality Management Target Items, and 102 types of agricultural chemicals are listed as matters for concern.
The water quality testing results up to the end of 2009 being made publicly available adhere to pre-revision water quality standards.
Detailed information in Japanese regarding water quality standards is available on the website of the Ministry of Health, Labour and Welfare.

( http://www.mhlw.go.jp/topics/bukyoku/kenkou/suido/kijun/index.html )

(1) Water Quality Standard Items

The items listed in the Water Quality Standard Items are determined on the basis of Article 4 of the Water Supply Law. Their values are set with full regard for safety, at levels that will have no effect on human health and will not impair the use of mains water in daily life.

Item		Standard Value�E�Eg/L�E�E/th>	Category	Outline	Main uses etc.
1	Standard plate count bacteria	100/ml or less	Indicator of disease-causing organisms	This indicator shows the general purity level of water and is usually extremely low. Detection of large quantities indicates the possibility of contamination by disease-causing organisms.
2	E. coli bacteria	Must not be detected	Indicator of disease-causing organisms	Exist in the intestinal tract of humans and animals and in the soil. Detection of E. coli in the water supply indicates the possibility of contamination by disease-causing organisms.
3	Cadmium and its compounds	0.003 or less	Inorganic substances and heavy metals	Widely distributed in nature together with zinc and lead in the form of mineral ores. Mine runoff and factory effluent are the major sources of river contamination. They mainly accumulate on the river bed.	Electroplate, plastic pigments, cadmium batteries, raw materials for ceramics, alloys
4	Mercury and its compounds	0.0005 or less		Exist in ore deposits, rarely found in rivers as a result of contamination by factory effluent. Inorganic mercury may be converted to methyl mercury by methanobacteria in environmental waters.	Dry batteries, fluorescent lights, thermometers, amalgam (dental or alloys), synthetic chemicals
5	Selenium and its compounds	0.01 or less		May be found in environmental water, mainly as contamination from mine runoff or factory effluent.	Semiconductor materials, photocells, solar batteries (rectifiers), pigments, alloys
6	Lead and its compounds	0.01 or less		Exist as mineral ores, and may be found in river water derived from geological features, factory effluent, or mine runoff. Often detected in the water supply, but this is mainly the result of leaching from lead pipes. Leaching is especially prevalent in soft water or water with a low pH.	Lead pipes and sheets, storage batteries, wire coating, solder, hardening agent for rubber type, matches
7	Arsenic and its compounds	0.01 or less		Exist as mineral ores. Rarely found in environmental waters, but may be present as a result of contamination by volcanic hot springs or mine runoff, factory effluent, or arsenic-containing agricultural chemicals.	Semiconductor materials, agricultural chemicals containing arsenate of lime or lead arsenate, preservatives, glass-working
8	Hexavalent chrome and its compounds	0.05 or less		Exist widely as chromium deposits. Have been known to contaminate groundwater through underground infiltration of plating runoff, but there are almost no examples of river water pollution.	Nichrome wires, stainless steel and other alloys, plating, batteries, tanning, preservatives
9	Cyanide ion and cyanogen chloride	0.01 or less		The cyanogen occasionally found in environmental waters comes from contamination with factory effluent from plating and other processes. Cyanogen chloride detected in the water supply is the result of the reaction between cyanogen and chlorine.	Insecticides and bactericides, electroplating
10	Nitrite nitrogen and nitrate nitrogen	10 or less		These increase as a result of the oxidation of nitrogen compounds present in nitrogenous fertilizers and decomposed animal and plant tissue. They are found in river water as a result of contamination with household wastewater or factory effluent. Because nitrates are converted to nitrites in the body, the water quality standard comprises the total of both nitrates and nitrites.	Inorganic nitrogenous fertilizers, explosives manufacture, food preservatives
11	Fluorine and its compounds	0.8 or less		Fluorine in environmental waters mainly comes from geological features or contamination by factory effluent. It may be particularly common in groundwater and rivers in hot-spring areas.	Aluminum electrolysis, tile bricks, glass fiber ceramics, semiconductor manufacture
12	Boron and its compounds	1.0 or less		Rarely found in environmental waters, but may be found in the form of metaboric acid in groundwater or hot springs in volcanic areas. It may also be found in seaweed, tea, and fruit.	Metal surface treatment agents, glass/enamel industry
13	Carbon tetrachloride	0.002 or less	General organic substances	Evaporates into the atmosphere when discharged into surface water, but may be detected in groundwater as a result of soil contamination or other sources.	Raw material for CFC manufacture, fumigation bactericides, metal cleaning solvents
14	1,4-Dioxane	0.05 or less		Does not exist in water in nature. When detected, its source has been factory effluent.	Solvents, stabilizer for solvents, surface treatment agents for artificial leather
15	Cis-1,2-Dichloroethylene and Trans-1,2-Dichloroethylee	0.04 or less		Evaporates into the atmosphere and easily undergoes photodecomposition when discharged into surface water, but may be detected in groundwater as a result of soil contamination or other sources.	Chlorinated solvents, intermediate in synthetic chemicals, solvents, lacquers
16	Dichloromethane	0.02 or less		Evaporates into the atmosphere when discharged into surface water, but may be detected in groundwater as a result of soil contamination or other sources.	Paint removers, cleaning agents, solvents
17	Tetrachloroethylene	0.01 or less		Evaporates into the atmosphere when discharged into surface water, but may be detected in groundwater as a result of soil contamination or other sources.	Dry cleaning solvents, oil-cleaning agents for metal
18	Trichloroethylene	0.03 or less		Evaporates into the atmosphere when discharged into surface water, but may be detected in groundwater as a result of soil contamination or other sources.	Oil-cleaning agents for metal, solvents
19	Benzene	0.01 or less		Evaporates into the atmosphere and decomposes when discharged into surface water. Undergoes biological decomposition in water. An aromatic solvent.	Pharmaceutical products, dyes, scents, raw material for synthetic resins, and others
20	Chloric acid	0.6 or less		Produced as a decomposition product when chlorine dioxide has been used as an oxidizing agent. Also generated by the oxidation of sodium hypochlorite.	Oxidizing agents, explosives
21	Chloroacetic acid	0.02 or less	Disinfection byproducts	When airborne is a byproduct of garbage incineration, but in environmental water is the result of the chlorination of effluent and other wastewater. Produced in the water supply as a result of chlorine treatment.
22	Chloroform	0.06 or less		Evaporates into the atmosphere and undergoes photodecomposition when discharged into surface water, and undergoes anaerobic biological decomposition in soil. One component of the trihalomethanes produced in the water supply as a result of chlorine treatment.
23	Dichloroacetic acid	0.04 or less		Found in the atmosphere as a decomposition product of trichloroethylene. In environmental waters it is the result of the chlorination of effluent and other wastewater. It is produced in the water supply as a result of chlorine treatment.
24	Dibromochloromethane	0.1 or less		Evaporates into the atmosphere and undergoes photodecomposition when discharged into surface water, and undergoes anaerobic decomposition in soil. One component of the trihalomethanes produced in the water supply as a result of chlorine treatment.
25	Bromate	0.01 or less		Produced by the oxidation of bromine present as an impurity during ozone treatment or the production of the disinfectant hypochlorous acid.	Flour enhancers, chemical hair treatments
26	Total trihalomethanes	0.1 or less		The total amount of chloroform, bromodichloromethane, dibromochloromethane, and bromoform is called “total trihalomethanes. E/td>
27	Trichloroacetic acid	0.2 or less		When airborne is a byproduct of garbage incineration, but in environmental waters is the result of the chlorination of effluent and other wastewater. Produced in the water supply as a result of chlorine treatment.
28	Bromodichloromethane	0.03 or less		Evaporates into the atmosphere and undergoes photodecomposition when discharged into surface water, and undergoes anaerobic biological decomposition in soil. One component of the trihalomethanes produced in the water supply as a result of chlorine treatment.
29	Bromoform	0.09 or less		Evaporates into the atmosphere and undergoes photodecomposition when discharged into surface water, and undergoes anaerobic biological decomposition in soil. One component of the trihalomethanes produced in the water supply as a result of chlorine treatment.
30	Formaldehyde	0.08 or less		Given off into the air by plastics and synthetic resins. In environmental waters its source is believed to be factory effluent or having been dissolved from plastic. In the water supply, it is produced by oxidation treatment such as ozone treatment.	Preservatives, raw materials for synthetic resins
31	Zinc and its compounds	1.0 or less	0.1 or less	Distributed as mineral ore such as zinc ore, but only found in trace concentrations in environmental waters. May be detected as a result of contamination by factory effluent or similar. A water quality standard has been set because if it is present at high concentrations water may turn cloudy when boiled.	Zinc-plated steel pipes
32	Aluminum and its compounds	0.2	Color	A metallic element widely present in soil, but due to its low solubility its concentration in environmental waters is low. It is used in waterworks as an aluminum flocculant during water purification treatment. The water quality standard is set because a high concentration causes turbidity.	Antacids, food additives, flocculants, metal materials
33	Iron and its compounds	0.3		Iron found in environmental water comes not only from geological features but may also derive from mine runoff, factory effluent, or other sources. A water quality standard has been set because when present at high concentrations iron compounds may cause an unpleasant taste or laundry staining.	Motor vehicles, pipes, construction materials, machinery
34	Copper and its compounds	1.0 or less		In nature occurs mainly in the form of ores such as copper pyrites. The threshold concentration at which it impairs water use is lower than the level at which it poses problems of toxicity, so the water quality standard is set from the standpoint of preventing the staining of laundry or other items.	Electric cables, alloys, coinage, statues, plating, agricultural chemicals
35	Sodium and its compounds	200 or less	Taste	An element that is widespread in environmental waters, it increases as a result of contamination with seawater, factory effluent, or other sources. In the water supply it is increased by the addition of water purification agents (such as sodium hydroxide). The water quality standard is set from the standpoint of taste.
36	Manganese and its compounds	0.05 or less	Color	May increase in environmental waters owing to contamination by factory effluent or mine runoff. The water quality standard is set from the standpoint of preventing impaired water use (black water).	Stainless steel, additives for specialty steels, dry batteries, oxidizing agents, pigments
37	Chloride ion	200 or less	Taste	Environmental waters always contain a certain amount of chloride ions (derived from geological features). In coastal regions, however, this may increase owing to the effect of seawater infiltration or other reasons. It may also increase as a result of contamination by sewage, household wastewater, factory effluent, or other sources. The water quality standard is set from the standpoint of taste.
38	Calcium, magnesium, etc. (hardness)	300 or less		The amount of calcium and magnesium ions in water is calculated from the amount of calcium carbonate (CaCO3) in mg/L. The hardness of environmental waters mainly depends on geological features. Water that is too hard may cause diarrhea and reduce the effectiveness of soap for cleaning, but an appropriate degree of hardness is believed to improve the taste of water.
39	Evaporated residue	500 or less		The solid substances left behind when water has evaporated, consists of the total of both matter suspended in the water and dissolved substances. The main components of evaporated residue include calcium, magnesium, silicic acid, sodium, and potassium chlorides.
40	Anionic surfactants	0.2 or less	Foaming	The active ingredients in synthetic detergents, in river water they come from contamination by factory effluent and household sewage. Their presence in water results in the formation of foam, and the water quality standard is set from the standpoint of preventing foaming.	Laundry and kitchen detergents, cosmetics
41	Geosmin	0.00001 or less	Musty smell	A substance that gives rise to the unpleasant odor (musty smell) generated by an overabundance of nutrients in lakes and other shallow waters. Even a small amount present in water causes a noticeable musty smell. It is produced by blue-green algae such as Anabaena.
42	2-Methyl-isoborneol	0.00001 or less	Musty smell	A substance that gives rise to the unpleasant odor (musty smell) generated by an overabundance of nutrients in lakes and other shallow waters. Even a small amount present in water causes a noticeable musty smell. It is produced by blue-green algae such as Phormidium and Oscillatoria.
43	Nonionic surfactants	0.02 or less	Foaming	Surfactants for which the active ingredient does not ionize in aqueous solution. In environmental waters they easily undergo biological decomposition. Their presence in water results in the formation of foam, and the water quality standard is set from the standpoint of preventing foaming.	Cleaning agents, moisturizing agents, emulsifiers, dispersive agents
44	Phenols	0.005 or less	Odor	Do not exist in waters in nature, but are contained in effluent from chemical factories and gas production plants. The presence of phenols results in the production of chloroform in water during the chlorine disinfection process, which can cause an unpleasant odor in the water supply. The water quality standard is set from the standpoint of preventing the generation of this unpleasant odor.	Synthetic resins, raw ingredients for surfactants and other agents
45	Organic substances (TOC)	5 or less	Taste	This refers to the total amount of carbon (TOC) present as organic substances in water, and is an index of the concentration of organic substances. It increases as a result of contamination by human waste, sewage, factory effluent, and other sources. Large amounts present in water can cause an unpleasant taste.
46	pH value	5.8-8.6	Basic properties	pH 7 is neutral, lower pH values indicate progressively increasing acidity, and higher pH values indicate progressively increasing alkalinity (basicity).
47	Taste	Must not be abnormal		The taste of water changes according to the types and concentrations of the substances dissolved in it as the result of the effect of geological conditions and other factors.
48	Odor	Must not be abnormal		The odor of water changes according to the types and amounts of the substances dissolved in it. Odors that are problematic for the water supply include a musty smell and chemical odors generated by chloroform and other substances.
49	Color	5 or less (color units)		This shows the degree of color of water. Values below the standard indicate that water is virtually colorless.
50	Turbidity	2 or less (turbidity units)		This shows the degree of cloudiness of water. Values below the standard indicate clear water with virtually no cloudiness.

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(2) Items for Water Quality Management Targets

Target values have been set for 27 items that are regarded as important for water quality management, including those that have been detected in the water supply but for which toxicity evaluation is still provisional and no water quality standard has yet been set, and those that may in the future be detected in the water supply at concentrations exceeding those for which water quality standards would become necessary.

Item		Target�E�Eg/l)	Category	Outline	Main uses etc.
1	Antimony and its compounds	0.015 or less	Inorganic substances and heavy metals	Mainly distributed as ores, but rarely present in environmental waters. May be detected as the result of contamination by mine runoff, factory effluent, or other sources.	Storage batteries, electric cables, combustion enhancers, paints
2	Uranium and its compounds	0.002 or less (provisional)		May be detected in environmental waters as a result of leaching from natural ore deposits.	Nuclear fuel, catalysts, colorants
3	Nickel and its compounds	0.01 or less (provisional)		Mainly distributed as ores, but rarely present in environmental waters. May be detected as the result of contamination by mine runoff, factory effluent, or other sources.	Stainless steel, plating, storage batteries
4	Nitrite nitrogen	0.05 or less (provisional)		These increase as a result of the oxidation of nitrogen compounds present in nitrogenous fertilizers and decomposed animal and plant tissue. They are found in river water as a result of contamination by household wastewater or factory effluent.	Food preservatives
5	1,2-Dichloroethane	0.004 or less	General organic substances	Evaporates into the atmosphere when discharged into surface water, but may be detected in groundwater as a result of soil contamination or other sources.	Raw material for vinyl chloride and synthetic resins, film cleaning agent
8	Toluene	0.2 or less		Evaporates extremely readily into the atmosphere when discharged into surface water. Undergoes biological decomposition in water.	Dyes, fragrances, explosives, gasoline additives
9	i (2-ethylhexyl) phthalate	0.1 or less		Has low solubility in water, but adheres readily to particles. Almost never hydrolyzed in environmental waters, but readily undergoes biological decomposition.	Plastic additives (plasticizers)
10	Chlorite	0.6 or less	Disinfection byproducts	May be detected as a decomposition byproduct when chlorine dioxide is used as a disinfectant.	Raw material for production of chlorine dioxide
11	Chlorate	0.6 or less		May be detected as a decomposition byproduct when chlorine dioxide is used as a disinfectant. Also produced by the oxidation of sodium hypochlorite.	Raw material for production of chlorine dioxide, oxidizing agents, explosives
12	Chlorine dioxide	0.6 or less		Readily decomposed in water into chlorite, chlorate, and chloride salts.	Disinfectants, leather cleaning agents, pulp whitening agents
13	Dichloroacetonitrile	0.01 or less (provisional)		May be detected in the water supply as a result of chlorine treatment.
14	Chloral hydrate	0.02 or less (provisional)		May be detected as a result of contamination by factory effluent. In the water supply, may be detected as a result of chlorine treatment.	Raw material for pharmaceuticals
15	Agricultural Chemicals	1 or less	Agricultural chemicals	The proportions of the amounts of individual agricultural chemicals detected are calculated with respect to their target values, and the total of these must be less than the target value of 1 for all monitored agricultural chemicals. Water quality management targets are set for 102 different agricultural chemicals shown in a separate table, and waterworks personnel can select the appropriate agricultural chemicals to measure from among these in line with their observations of local situations. In Osaka City, the levels of 99 different agricultural chemicals are measured.
16	Residual chlorine	1 or less	Odor	Chlorine treatment is carried out by waterworks, and a specified level of residual chlorine must be maintained in the water supply. Residual chlorine refers to the active chlorine remaining in water after its chlorination, and is categorized into free residual chlorine and combined residual chlorine. A small amount of residual chlorine is practically unnoticeable, but at high concentrations water has an unpleasant taste and smells of chlorine.
17	Calcium, magnesium, etc. (hardness)	Between 10 and 100, inclusive	Taste	The amount of calcium and magnesium ions in water is calculated from the amount of calcium carbonate (CaCO3) in mg/L. The hardness of environmental waters mainly depends on geological features. Water that is too hard may cause diarrhea and reduce the effectiveness of soap for cleaning, but an appropriate degree of hardness is believed to improve the taste of water.
18	Manganese and its compounds	0.01 or less	Color	May increase in environmental waters owing to contamination by factory effluent or mine runoff. The water quality management target is set from the standpoint of preventing impaired water use (black water) and providing an even higher quality water supply.	Stainless steel, additives for specialty steels, dry batteries, oxidizing agents, pigments
19	Free carbon dioxide	20 or less	Taste	This refers to the carbon dioxide (CO2) dissolved in water. It is present in large quantities in groundwater owing to its production in the decomposition of organic matter and other reactions. Free carbon dioxide gives water a fresh, pleasant taste, but in large quantities it gives it an astringent taste and makes it less mellow.
20	1,1,1-Trichloroethane	0.3 or less	Odor	Evaporates into the atmosphere when discharged into surface water.	Metal cleaning, dry cleaning solvent
21	Methyl tertiary-butyl ether (MTBE)	0.02 or less	General organic substances	Can be detected in groundwater as it dissolves well in water and does not evaporate easily. The target value is set from the standpoint of preventing unpleasant taste and odor.	Gasoline octane improver, low-boiling-point solvent
22	Organic substances, etc. (potassium permanganate consumption)	3 or less	Taste	These increase as a result of contamination by sewage or factory effluent, and are therefore used as a pollution index together with biological oxygen demand (BOD) and other parameters.
23	Threshold odor number (TON)	3 or less	Odor	A value indicating the greatest dilution with odor-free water that still yields a just-detectible odor, this index indicates the strength of the odor. It is used to investigate odors other than the smell of chlorine.
24	Evaporated residue	Between 30 and 200, inclusive	Taste	The solid substances left behind when water has evaporated, consists of the total of both matter suspended in the water and dissolved substances. The main components of evaporated residue include calcium, magnesium, silicic acid, sodium, and potassium chlorides, and organic substances.
25	Turbidity	1 or less (turbidity units)	Basic properties	This indicates the degree of cloudiness of water, so the water quality management target is set from the standpoint of providing an even higher quality water supply.
26	pH value	Around 7.5 (pH units)	Corrosion	pH 7 is neutral, lower pH values indicate progressively increasing acidity, and higher pH values indicate progressively increasing alkalinity (basicity).
27	Causticity (Langelier index)	Should be around -1 or above, and as close to 0 as possible.	Corrosion	This index determines the level of corrosivity of metal or concrete by water. The more highly negative the value, the more corrosive the water.
28	Heterotrophic bacteria	2000/ml or less (provisional)	Index of cleanliness at water service facility	Heterotrophic bacteria indicate bacterial count in water attributable to the formation of biofilm and other substances in distribution pipes, etc., so as an index it indicates the level of purity at a waterworks facility.
29	1,1-Dichloroethylene	0.1 or less	General organic substance	Evaporates into the atmosphere and easily undergoes photodecomposition when discharged into surface water, but may be detected in groundwater as a result of soil contamination or other sources.	Raw material for vinylidene chloride resin manufacture
30	Aluminum and its compounds	0.1 or less	Color	A metallic element widely present in soil, but due to its low solubility its concentration in environmental waters is low. It is used in water supply as an aluminum flocculant during water purification treatment. The water quality standard is set because a high concentration causes turbidity.	Antacids, food additives, flocculants, metal materials

Produced with reference to the Dictionary of Water Works Terminology published by the Japan Water Works Association and the List of Resources Providing Evidence Concerning Items (Chemical Substances) Being Considered for Revisions to Water Quality Standards published by the Ministry of Health, Labour and Welfare. Item 6, 7 and 11 of the Water Quality Management Targets has been deleted from the new Water Quality Standards of FY2010and other places.

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